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SubjectRe: [PATCH] isdn: mISDN: tei: Fix a sleep-in-atomic-context bug in create_teimgr()
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Hi,

I do not understand the analysis and do not see that the spinlock is a
problem here.
I think your DSAC analyzer assumes that the FUNC_PTR mgr_ctrl call calls
the mgr_ctrl in tei.c, but in real it calls l2->ch.ctrl() which is the
function in layer2.c, not tei.c. And the function in layer2.c should not
do any GFP_KERNEL allocation.

Same for your 2. reported issue.

Am 01.09.2018 um 14:00 schrieb Jia-Ju Bai:
> The kernel module may sleep with holding a spinlock.
>
> The function call paths (from bottom to top) in Linux-4.16 are:
>
> [FUNC] kzalloc(GFP_KERNEL)
> drivers/isdn/mISDN/tei.c, 1058: kzalloc in create_teimgr
> drivers/isdn/mISDN/tei.c, 1278: create_teimgr in mgr_ctrl
> drivers/isdn/mISDN/tei.c, 1048: [FUNC_PTR]mgr_ctrl in create_teimgr
> drivers/isdn/mISDN/tei.c, 1045: _raw_read_lock_irqsave in create_teimgr
>
> Note that [FUNC_PTR] means a function pointer call is used.
>
> To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.
>
> This bug is found by my static analysis tool DSAC.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> ---
> drivers/isdn/mISDN/tei.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/isdn/mISDN/tei.c b/drivers/isdn/mISDN/tei.c
> index 12d9e5f4beb1..6d95ee639fdb 100644
> --- a/drivers/isdn/mISDN/tei.c
> +++ b/drivers/isdn/mISDN/tei.c
> @@ -1055,7 +1055,7 @@ create_teimgr(struct manager *mgr, struct channel_req *crq)
> crq->adr.tei, crq->adr.sapi);
> if (!l2)
> return -ENOMEM;
> - l2->tm = kzalloc(sizeof(struct teimgr), GFP_KERNEL);
> + l2->tm = kzalloc(sizeof(struct teimgr), GFP_ATOMIC);
> if (!l2->tm) {
> kfree(l2);
> printk(KERN_ERR "kmalloc teimgr failed\n");
>

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